The present invention relates to signs, and particularly to outdoor signs of the type which generally indicate in digital form time and temperature. Heretofore, such signs have commonly comprised banks of lamps which are selectively energized to display alternately time and/or temperature information.
Lamp bank signs require a substantial amount of electrical energy to operate because they must be continuously electrically energized, and to reduce the amount of electrical energy necessary to operate such signs it has been proposed to replace the banks of indicating lamps with pivotally mounted discs brightly colored on one side and generally black on the opposite side. For daytime use, the brightly colored side is readily visible under ambient light conditions. For nighttime use, a light source is directed upon the front face of the sign to brightly illuminate the brightly colored sides of the indicating discs facing forwardly. Each indicating disc is attached to a permanent magnet mounted for rotation upon an axis lying in a plane parallel to the viewing plane of the sign involved. In one form of such sign described in U.S. Pat. No. 3,518,664, the permanent magnets are bar magnets each of which extends between a pair of the vertically spaced electromagnet core legs extending transversely of a vertical support panel. When an electromagnet is momentarily energized with a current of a given desired polarity, an opposing magnetic field is generated which generally causes the adjacent bar magnet to move into an opposite position provided the electromagnet produces a net turning torgue. Although usually slight unsymmetrical weight distributions ensures that a net turning torgue is generally produced, such is not always the case.
In the magnetically operated flip disc sign of U.S. Pat. No. 3,518,664, indicating disc stops are provided for limiting the angle of rotation of bar magnets and associated indicating discs to less than 180.degree., which would normally prevent the magnetic axes of the bar magnets from being aligned with the core legs so as to assure the development of a net turning torgue on the permanent magnets when the associated electromagnets are energized. However, due to the presence of biasing magnets, the magnetic axes to which the bar magnets tend to become aligned upon energization of the associated electromagnets are inclined to a line between the ends of the associated pairs of core legs, and the bar magnets become oriented in perfect alignment with such magnetic axes. However, the energization of an electromagnet produces a resultant magnetic field which is misaligned with the bar magnet field in a direction to rotate the same way from its associated stop.
The various magnetically operated flip disc signs heretofore proposed left much to be desired from the standpoint of their reliability, space occupied thereby, and the cost of constructing and operating the same. A common objective of the designers of such signs is to minimize the amount of electrical power necessary to flip each permanent magnet when an electromagnet is energized momentarily.
It is thus an object of the invention to provide a magnetically operated sign having banks of permanent magnet-carrying indicating discs or the like as above described where the amount of electrical energy needed to flip an indicating disc from one position to another is minimized.
Another object of the invention is to provide a magnetically operated sign comprising permanent magnet-carried indicating discs or the like wherein the sign can be reliably constructed at less cost than the magnetically operated flip disc sign heretofore constructed.
Still another object of the invention is to provide a magnetically operated sign similar in some respects to that shown in U.S. Pat. No. 3,036,300, where the electromagnet which operates each permanent magnet has only a single core leg extending horizontally from a support panel, with the permanent magnet confronting the front face of such core, so that the electromagnet can be of a very simple and compact construction, and further wherein the sign operates more reliably and preferably with the more efficient use of electrical energy. A further object of the present invention is to provide a magnetically operated flip disc sign where the different parts thereof are constructed so that they can be more easily assembled and dis-assembled for servicing or relocation than prior magnetically operated flip disc signs.